High virulence is..

better able to cause disease

Pathogenesis

how the disease develops

Pathogen

organism that can cause disease (bug)

Infection

invasion or colonization of the body by pathogenic organisms

Disease

abnormal state where the body is not capable of performing normal functions

10

Typical human body has approx...

1 x 10^13 human cells

11

Transient microbiota

microbes that may be present for days or months and then disappear

12

Microbiota is ..

localized in certain regions of the body. generally found in exposed areas (skin, urinary tract, etc)

13

Microbial antagonism

members of the microbiota produce substances harmful to invading microbes

14

Competitive exclusion

microflora use up available nutrients preventing the growth of pathogens

15

Benefits of microbiota

-E.coli in large intestine makes vitamin B and B-produce enzymes that aid digestion

16

Opportunistic pathogens

microbes that are part of the normal microbiota and don't normally cause disease

17

Opportunistic pathogens can cause disease if..

-they are transferred to another part of the body-the human host becomes immunocompromised -if normal microbiota is disturbed

18

Example of opportunistic pathogen

E.coli is normal resident of large intestine tract but transferred to urinary can cause infection

19

Symptoms

what patient feels. subjective and variable

20

Signs

objective change that a physician can measure

21

Syndrome

specific group of signs and symptoms that always accompany a particular disease

22

Communicable disease

that spreads from one host to another

23

Contagious disease

easily spread

24

Non-communicable disease

doesn't spread between hosts

25

Incubation period

time between the infection and first sings or symptoms

26

Prodromal period

early and mild symptoms such as malaise (feeling of unwell)

27

Period of illness

most serve signs and symptoms. active immune response may cause some sings and symptoms

28

Period of decline

sings and symptoms subside. can last for hours or days. patient is vulnerable to secondary infections

29

Period of convalescence

recovery occurs. pathogen may still be present and spread to others. person can continue to carry the pathogen for months

30

A infection can be spread in what sae?

every stage

31

Acute

rapidly developing, short duration

32

Chronic

slow to develop, continual duration

33

Latent

inactive for a period of time, can be reactivated

34

Infectious dose (ID50)

amount of bacteria required to cause disease in 50% of the population

35

Greater ID it is..

weaker it is

36

Lethal dose (LD50)

amount of toxin needed to be given to cause death in 50% of its recipients.

37

Local infection

confined to a small area of the body

38

Systematic infection

microbes or toxins are spread throughout the body

39

Septicemia

systemic infection of the blood

40

Bacteremia

bacteria in blood

41

Toxemia

toxins in the blood. need a bacteria to cause this toxin

42

Viremia

virus particles in the blood

43

Sepsis

life threatening systemic inflammatory response, usually due to bacteremia. results in shock and lethal

44

Koch's postulates

were developed based on the germ theory of disease, allow the determination of specific microorganisms that cause disease

45

4 rules of Koch's postulates

-same pathogen should be present in every case-pathogen must be isolated and grown in pure culture-pathogen from the pure culture should cause disease when its inoculated into a healthy lab animal-same microbe should be isolated again from individual that was inoculated

46

Exceptions of Koch's postulates

-some bacteria will not grow in pure culture-some pathogens cannot be used to infect lab animals-sometimes several diff microorganisms can cause the same disease-sometimes one pathogen can cause many diff diseases

47

Adherence

surface molecules that allow a pathogen to stick to the surface, often stick to a specific receptors on the host cell surface

48

Invasiveness

ability of a pathogen to invade and multiply in healthy tissues

49

2 types of molecules that promote invasiveness

-extracellular enzymes-invasins

50

Extracellular enzymes (exoenzymes)

these enzymes erode the surface of host cells and damage tissue. products of degradation are used for food and protect from host defences

51

3 types of extracellular enzymes

-fibrinolysin-collagenase-coagulase

52

Fibrinolysin

degrades fibrin clots

53

Collagenase

degrades connective tissue

54

Coagulase

promotes blood clots around the bacterial cell

55

Invasins

surface proteins that cause the rearrangements of the host cell cytoskeleton, forces host cell to take in bacterium and be protected from host defences

56

Germs must first penetrate...

host defences in order to damage tissues and go on to cause disease

57

Respiratory tract

most common portal of entry, microbes inhaled into nose of mouth

58

Gastrointestinal tract

germs enter in food or water, most are destroyed by the acid of stomach or bile of intestine

59

Genitourinary tract

sexually transmitted infection

60

Most pathogens required a..

broken mucous membrane (a cut)

61

Skin

unbroken skin is impenetrable by most microbes. some can gain access through hair follicles while others require wound (grow on skin like fungi)

62

Parenteral route

microbes deposited directly into tissues when skin or membranes are broken

63

Parenteral =

injection/inoculation

64

Indirect damage to host

inducing an immune response and causing inflammation

65

Direct damage to host

production of exoenzymes or toxins

66

Toxin

poisonous substance produced by a microorganism

67

Toxoid

inactive toxin, can be used as vaccine

68

Exotoxins

toxins which are secreted from the bacterial cell, heat sensitive, can be extremely toxic